A light emitting diode (LED) device is a compound semiconductor device which converts electrical energy into light energy. The LED may implement various colors by adjusting a composition ratio of a compound semiconductor.
When compared to existing light sources such as a fluorescent lamp and an incandescent lamp, a nitride semiconductor LED has advantages, such as lower energy consumption, semi-permanent life span, rapid response speed, stability, and environmental friendliness. Accordingly, an application range of the nitride semiconductor LED has been extended to LED backlights capable of replacing a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) device, white LED lighting devices capable of replacing a fluorescent lamp or an incandescent lamp, vehicle headlights, and signal lamps.
Generally, a gallium nitride-based LED is grown on a sapphire substrate. However, since a sapphire substrate is hard and electrically nonconductive and has low thermal conductivity, a sapphire substrate is faces limitations in reducing manufacturing costs through size reduction of the gallium nitride-based LED and improving light output and characteristics of a chip.
In existing InGaN LEDs grown on a sapphire substrate, a silicon carbide substrate, a silicon substrate, and the like, a droop phenomenon in which internal quantum efficiency decreases as current density increases may occur, and reliability problems such as current crowding may occur.
Therefore, in order to develop an LED having characteristics such as high efficiency and high current, there is a need to develop an LED using a GaN bulk substrate having a small lattice mismatch and low dislocation density.